Fault location methods at compensated MV networks

Major advantages of compensated networks are the self-extinction of arcing faults and that the RMS of the single phase to ground (SPG) fault current is small, and therefore the fault can theoretically be allowed to persist for several hours. The continuous operation of the system can be sustained during a SPG fault in order to continuously supply the consumers if the touch voltage at the poles remains small. A great disadvantage of compensated networks, however, is the complicated way a SPG fault can be located. The first part of this paper contains a short review on problems related to distribution system operators´ (DSOs) current practice regarding Earth fault location and sustained faulty operation of compensated networks. Some fault localization methods published in the literature will then be shortly summarized and compared based on computer simulation using EMTP software. Advantages and disadvantages of different methods will be shown. An innovative device and method will be presented that was implemented at two Hungarian DSOs. An evaluation of the operation experience will be given based on real field measurement data. The main contribution of the paper is the proposal for a fault location method that greatly increases system reliability indices and is therefore economically feasible in most distribution systems.